Last week, after more than a month of avoiding the media, Sen. John Kerry (D-Mass.) sat down with Time magazine’s Karen Tumulty and announced, “I don’t know what you’re talking about in terms of the Bush bounce.” We haven’t seen this kind of denial from a presidential candidate since Gerald Ford “freed” Poland in a 1976 presidential debate. [IMGCAP(1)]

Maybe Kerry was still waiting for his bounce, or maybe he actually believed his own handlers, who had argued prior to the Republican convention that a Bush bounce wasn’t likely because the country was too polarized to have any swing voters left.

But the Bush campaign did the strategically smart thing: to be first to engage swing voters using one of the most high-profile avenues available to them, the convention. After being told by Democratic spinners and many media pundits that the prime-time speakers did not represent the “true” Republican Party, Americans saw something quite different. They saw a unified convention enthusiastically cheering the speeches of Rudy Giuliani, Sen. John McCain (R-Ariz.) and Arnold Schwarzenegger. These speakers, along with President Bush, delivered a message to the middle that has changed the dynamic of the election and left the Kerry campaign floundering amid major personnel and strategy changes.

So, where are we, now that both conventions are history? What we have seen is a significant shift in the electorate. For months, voters moved very little. But the past two weeks have shown that, contrary to popular belief, many voters are indeed in play. And a large portion of them “swung” to Bush after his convention.

Let’s go to the numbers. First, using registered voters instead of likely voters — which I believe gives a more accurate picture — the change in favor of Bush ranges from plus-15 in a Time Magazine poll to plus-4 in the AP/IPSOS poll.

But more than just the ballot test is changing. This shift is structural. For example, the most recent job approval numbers show Bush has come back to 50 percent or higher in almost all major surveys.

Perhaps the most troubling numbers for the Kerry campaign, however, are the favorable-unfavorable numbers for the candidates. Here Bush has taken a significant lead in most polls. Even more troubling for the Democrats, Kerry’s image has become either neutral or negative in several of these polls.

With numbers like these, it’s no wonder that Kerry seems to be having a small problem with reality.

So what did the conventions mean?

1.) First, we now know there is a Big Middle.

Democrats believed that because they didn’t receive a bounce from their convention, the Republicans wouldn’t either — that is, that the electorate is so polarized that neither side has room for movement. Strategically, that translated into everything being about turning out the base.

However, Bush’s bounce after the Republican convention shows that people are still making up their minds, and that both candidates have to compete for the middle vote. William Safire wrote in The New York Times that the movement in polls since the GOP convention “means the old ‘swing vote’ still swings, and the battle for voters is in the political center.”

2.) The Democratic convention was a missed opportunity for Kerry.

The best opportunity Kerry had to speak to swing voters — his convention — has now been squandered. He spent his convention introducing himself, predominantly outlining his Vietnam service rather than laying out an agenda or spending much time speaking to the issues that swing voters are concerned about. Granted, he can still address these issues in the debates, but he failed to use his best bully pulpit to his advantage. By the time the debates roll around in a few weeks, it may be too little, too late.

3.) The Bush bounce has changed the dynamics of the race — from a state-by-state focus to a national focus.

If Bush maintains a lead of five points or more, the size of this lead means that Kerry will have to move demographic groups at a national level instead of incremental moves in targeted states. Even the most marginal popular-vote advantage can translate into major payoffs in the electoral college.

• In 1988, George H.W. Bush beat Michael Dukakis by 7 points, 53-46, but he received 426 electoral votes compared to Dukakis’ 111.

• In 1992, Bill Clinton won by only a margin of 6 points, 43-37, but he won 370 electoral votes in contrast to 168 for Bush.

If the present lead holds, the Kerry camp will need to rethink their campaign strategy — fast.

David Winston is president of The Winston Group, a Republican polling firm.